In order to support high-capacity data services, a wireless communication system that uses a high-frequency band such as, for example, a millimeter wave (mmW) is considered as the next-generation wireless communication system. In the case of the system that uses a high-frequency band, the available communication distance between a Mobile Station (MS) and a Base Station (BS) is short, so a cell radius of the BS is small, causing an increase in the number of BSs installed to secure the service area (or service coverage) for the MS. When the mobility of the MS is taken in consideration, if the cell radius of the BS is reduced and the number of BSs increases, the number of inter-cell handovers of the MS increases, and the system overhead may increase due to the frequent handovers of the MS.
In this wireless communication system using a high-frequency band, the number of BSs per unit area may increase. In this case, while an MS moves from place to place, the serving BS in communication with the MS may be changed or replaced frequently, and an authentication procedure for generating and allocating an authentication key or a security key for data exchange or data transmission/reception between the changed BS (to which the MS is handed over) and the MS is required whenever the serving BS is changed. Therefore, there is a need for a method for efficiently performing the authentication procedure in the wireless communication system that uses a high-frequency band.